Simplify the expression. $(5a^{4}+5a^{3}-7a^{2})(4a^{4}-2a)$
Answer: First use the distributive property. $ 5 a^4 (4 a^4) + 5 a^4 (-2 a) + 5 a^3 (4 a^4) + 5 a^3 (-2 a) - 7 a^2 (4 a^4) - 7 a^2 (-2 a) $ Simplify. $20a^{8}+20a^{7}-28a^{6}-10a^{5}-10a^{4}+14a^{3}$